Combustion and carbon monoxide in e cigs?

An another thread, another ECF member posted an opinion that combustion is actually occurring in atomizers, causing carbon monoxide to be produced when inadequate airflow was occurring (incomplete combustion) - which seemed to be an erroneous statement, as atomizers (though a misnomer - eliquid is only vaporized, not atomized) do not, or should not be producing any combustion whatsoever.

It prompted me to do some more research, and respond. But since the thread is with regard to atomizer modification and does not get much attention, I thought I'd post my comments/concerns/opinion here.

The following is more or less what I replied with in the other post. It is my take on what is occurring in the atomizer (vaporizer) with regard to the main ejuice components, and why I believe it is incredibly improbable if not impossible that any combustion is occurring.

This is based on my own scientific knowledge and a few hours of research I did late last night:

If anyone has any questions or comments or sources of relevant information, please post. And if anyone disagrees or knows that anything in my post is incorrect, please let me know. It was late and I was using a number of web sources for temperature information such as the flash points and autoignition values for the chemicals involved.

Oxygen in itself is not combustible, it has to be combined with a fuel source. Oxygen promotes (and is required for) combustion. An atomizer is merely a heating element, like a toaster or an electric stove. Ejuice is not intended to be a fuel source.

VG has a flash point of 390F, and PG a flash point of 210F. Granted, above these temps, they COULD become fuel sources and would combust if combined with oxygen... and an ignition source.

At around 250+/-F, the atomizer should be rapidly vaporizing PG and VG less rapidly (unless atomizers are reaching temps above 390F, in which case the VG would also rapidly vaporize).

If there were an ignition source (open flame) in an ecig (or possibly if the device is malfunctioning and creating a spark), the PG and/or VG could combust.

There should not be any combustion happening in a properly functioning vaporizer, all the necessary ingredients are there except an ignition source. The ignitable mixture is explosive, and if it were combusting, I would expect flames would be shooting out of people's devices.

The autoignition temperatures of both PG and VG are around 700 degrees F (PG 700F, VG 698F) - it is extremely unlikely that even a malfunctioning atomizer is reaching those temps.

The products of PG combustion are carbon dioxide and water, so even if combustion were to take place, it would be relatively harmless - though some research papers claim that an acrid smoke is also produced. I don't know if incomplete combustion of PG will create CO, as can happen with other hydrocarbons, but it is certainly a possibility whenever a hydrocarbon is burned without adequate oxygen. Once again, combustion shouldn't be taking place, the liquid should merely be vaporizing rapidly (albeit into a potentially ignitable mixture).

If combustion of Glycerol (VG) were to occur, then Acrolein would be produced - ACROLEIN IS EXTREMELY TOXIC, A PULMONARY IRRITANT - IT WAS USED AS A CHEMICAL WEAPON DURING WWI!

VG also decomposes into acrolein at temperatures above 536F.

Since it is highly unlikely that VG is being combusted, or reaching temperatures high enough to make it decompose, there should not be any acrolein being produced.

If acrolein were being produce, I imagine most vapers would already be dead.

As long as the atomizer isn't reaching temps of 280C/536F, and as long as there is no spark or open flame to combust the ignitable mixture, there should be no combustion (therefore no possibility of CO) and no other toxic products (from VG or PG).

So vape away.

Of course, it would be quite difficult to evaluate all the potentially dangerous products or combustibility temperatures of all ejuice components, because there are so many flavors, containing AT LEAST one additional chemical for every flavor added. I seriously doubt, though, that any of them are reaching their autoignition temperatures. I would be more concerned with whether or not the flavor chemicals can be absorbed by the lungs, and maybe what they decompose into and at what temperatures.

I was showing coworkers my ecig and I was confronted with several questions that forced me to do similar research on my own. I have come to the same conclusions that you reached. Some of my numbers were slightly different (must be from our sources) but in general they were close and the end results were the same as mine.

I was showing coworkers my ecig and I was confronted with several questions that forced me to do similar research on my own. I have come to the same conclusions that you reached. Some of my numbers were slightly different (must be from our sources) but in general they were close and the end results were the same as mine.